This disclosure relates in general to electrical switches and, more specifically, to a remote switching system using a radio frequency identification signal to convey a switch state.
Conventional switches are generally connected to electrically controlled devices by two or more insulated wires. Many devices including lights, motors, engines, vehicle safety systems, lawn and garden shutdown systems, fans, heaters, controllers, and numerous other devices are controlled by conventional switches. The wires connected to the switches typically carry the electricity that drives an electrical device or carries a switching signal that controls the device.
The wires that power lights in a building are routed to the switch and to the light. The additional length of the wires that are routed to the switch adds to the cost of the building. The wires are extended through walls, requiring holes through studs, and threading the wires through the holes.
In control systems for vehicles, such as automobiles, boats, tractors, and lawn and garden equipment, wires are routed from control switches and sensing switches to the device being controlled. The wiring harnesses used in vehicles account for a significant portion of the cost of the vehicle.
Small battery powered remote controls using radio frequency signals or infrared signals to control devices have been developed. These devices are commonly used to control audio and video entertainment equipment, garage door openers and doorbells. One drawback to battery powered remote controls is that the battery""s charge eventually runs out. Battery powered remote controls are not suitable for many applications, because a drained battery can be very inconvenient and even unsafe.
U.S. Pat. No. 5,163,112 to Lefevre et al. discloses a remote switch system for controlling electrical devices using an optical fiber to communicate the controlling signal from the remote switch to the device. Although the switch disclosed by the Lefevre et al. patent uses only one small optical fiber rather than two or more wires, the fiber optic fiber still has to be routed from the switch to the device being controlled.
There is a need for an improved system for switching electrically controlled devices that does not require a physical connection between the switch and the device, does not require a physical connection to a power source and does not require batteries.
The present invention concerns a self-contained radio frequency powered switch. The radio frequency powered switch includes a switch housing, a radio frequency powered circuit and a switch actuator. The radio frequency powered circuit is enclosed within the switch housing. The actuator extends into the switch housing and is movable between a first and a second position. The radio frequency powered circuit transmits a signal when the actuator is in the first or second position. Movement of the switch actuator to the other position alters the signal transmitted by the radio frequency identification integrated circuit. In one embodiment, the radio frequency powered circuit is a radio frequency identification integrated circuit (RFIDIC).
In one embodiment, an antenna is connected to the radio frequency identification integrated circuit. Movement of the actuator alters an electrical connection between the antenna and the radio frequency integrated circuit to alter the signal. A variety of mechanisms may be employed to alter the connection between the antenna and the radio frequency identification integrated circuit to alter the signal provided by the RFID switch. The antenna may be detuned by shorting antenna detuning leads. The ability of the radio frequency identification integrated circuit to detune the antenna may be disabled by opening the detuning lead from the radio frequency identification integrated circuit to the antenna. The antenna may be shorted to disable the power to the integrated circuit and the ability of the integrated circuit to communicate. The lead from the antenna to the integrated circuit may be opened to disable the integrated circuit power supply and the ability of the chip to communicate. A switch input to the integrated circuit may be provided that causes the integrated circuit to communicate a different value to the reader.
In one embodiment, the antenna is selectively shielded. Selectively shielding the antenna allows the signal to be provided when the actuator is in one position. The signal is blocked when the actuator is in a second position.
A variety of mechanisms may be employed for communicating the position of the actuator to the RFID integrated circuit or antenna. For example, a magnetic field may be employed to open and close connections to leads of the radio frequency identification integrated circuit. A reed switch or a hall switch may be coupled to leads of the integrated circuit. Movement of the actuator with respect to the reed switch or a hall switch alters the magnetic field at the reed switch or hall switch to open or close a connection to an input to the integrated circuit.
Traditional contacts may also be used to open and close inputs to the integrated circuit and/or the antenna. For example, a dome contact, wiping contact, point contact or leaf contact may be employed to open or close connections to the integrated circuit and/or the antenna.
A variety of switch types may be constructed as radio frequency identification integrated circuit switches. Examples of switches that can be constructed using the radio frequency identification integrated circuit switch design include rocker switches, push button switches, toggle switches, rotary switches, slide switches, tact switches, trigger switches, thumbwheel switches, push/pull switches, limit switches, lever switches, and conventional wall switches.
In use, the actuator is moved to one of the first position and the second position. In at least one of the positions, the radio frequency identification integrated circuit transmits a signal. The actuator is moved to the other position to alter the signal.
In one embodiment, the radio frequency identification switch is used in a radio frequency identification control system. The control system includes an oscillator, an RFID switch, and a data detection circuit. The oscillator produces a radio frequency carrier signal that powers the radio frequency identification integrated circuit of the RFID switch. The data signal detection circuit detects the data signal transmitted by the RFID switch and provides an output that is indicative of a position of the switch actuator. The output from the data signal detection circuit may be used to control virtually any device that is controlled by a conventional switch.
When the radio frequency identification control system is used, a radio frequency carrier signal is produced. The carrier signal is received by the radio frequency identification integrated circuit that is enclosed in the switch housing. The carrier signal powers the radio frequency identification integrated circuit. In one position, a data signal is transmitted with the radio frequency identification integrated circuit. When the actuator of the RFID switch is moved to the other position, the signal is altered. The data signal is received by the data signal detection circuit. The data signal detection circuit provides an indication of the position of the actuator.
Additional features of the invention will become apparent and a fuller understanding will be obtained by reading the following detailed description in connection with the accompanying drawings.